In diesel engines, air is drawn into a combustion chamber during an intake stroke by opening one or more intake valves. Then, during the subsequent compression stroke, the intake valves are closed, and a reciprocating piston of the combustion chamber compresses the gases admitted during the intake stroke, increasing the temperature of the gases in the combustion chamber. Fuel is then injected into the hot, compressed gas mixture in the combustion chamber, resulting in combustion of the fuel. Thus, in a diesel engine, the fuel may combust with the air in the combustion chamber due to the high temperature of the air, and may not be ignited via a spark plug as in a gasoline engine. The combusting air-fuel mixture pushes on the piston, driving motion of the piston, which is then converted into rotational energy of a crankshaft.
However, the inventors have recognized potential issues with such diesel engines. As one example, diesel fuel may not mix evenly with the air in the combustion chamber, leading to the formation of dense fuel pockets in the combustion chamber. These dense regions of fuel may produce soot as the fuel combusts. As such, conventional diesel engines include particulate filters for decreasing an amount of soot and other particulate matter in their emissions. However, such particulate filters lead to increased cost and increased fuel consumption.
Modern technologies for combating engine soot output include features for entraining air with the fuel prior to injection. This may include passages located in the injector body, as an insert into the engine head deck surface, or in engine head. Ambient air mixes with the fuel, cooling the injection temperature, prior to delivering the mixture to the compressed air in the cylinder. By entraining cooled air with the fuel prior to injection, a lift-off length is lengthened and start of combustion is retarded. This limits soot production through a range of engine operating conditions, reducing the need for a particulate filter.
However, the inventors herein have recognized potential issues with such injectors. As one example, the previously described fuel injectors may no longer sufficiently prevent soot production to a desired level in light of increasingly stringent emissions standards. As such, particulate filters may be located in an exhaust passage, thereby increasing a manufacturing cost and packaging restraint of the vehicle.
In one example, the issues described above may be addressed by a system comprising a combustion chamber comprising a duct comprising at least one flow-through passage configured to receive a fuel injection and combustion chamber gases, the flow-through passage comprising a first diameter upstream of and larger than a second diameter, the second diameter upstream of and larger than a third diameter, and where a first difference between the first and second diameters is greater than a second difference between the second and third diameters. In this way, soot production is limited or prevented when pre-combustion is detected in the passage.
As one example, the flow-through passage is integrated into one or more of a duct and nozzle tip of the fuel injector. The first diameter corresponding to an inlet of the flow-through passage and the third diameter corresponding to an outlet of the flow through passage. Additionally or alternatively, the first diameter may be the largest diameter of the flow-through passage and the third diameter may be the smallest diameter of the flow-through passage. This may provide the flow-through passage with a substantially trumpet-shape. By doing this, a duration of time a fuel injection resides in the flow-through passage may be decreased relative to flow-through passage having a fixed diameter. In this way, particulate matter output may be mitigated and/or prevented.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.